1. Field of the Invention
This invention relates to a composition usable in an infrared decoy flare to decoy advanced "two color" discriminating missiles.
2. Description of the Related Art
Decoys in the radar and infrared bands are used by aircraft to protect against approaching missiles. Devices are known, for instance, for aircraft to dispense chaff and IR flares. This chaff is intended to act as decoy for radar and/or increase ground clutter at the same time. However, modern pulse-doppler radar can recognize such decoys, especially in the lookdown/shootdown mode. This is particularly true because simple decoys, in contrast to true targets, do not exhibit a corresponding doppler shift in the radar band. A second problem is caused by the fact that prior infrared flares as point source Magnesium/PTFE flares either exhibit an entirely inappropriate adaptation of the aircraft's IR radiation and, moreover, radiate excessively in the UV band, or when they function as area flares on the basis of red phosphorus, they can not only be recognized as such because of the absence of independent motion, but because they do not emit their IR radiation until after they are beyond the sighting window of the IR searchhead which is locked onto the true target. In addition, flares will also be ineffective against imaging searchheads expected to be available in the future because such decoys, in contrast to true targets, exhibit no contours or edges in the low-frequency range.
An aircraft able to recognize the illumination of a hostile fighter through its lookdown/shootdown aircraft radar, nevertheless cannot know whether the enemy is employing missiles with a passive IR searchhead and/or with a passive radar searchhead, which uses the target's reflection in the illumination radar as target information.
A flying decoy is disclosed in U.S. Pat. No. 3,866,226 as launched from an aircraft, and as having a streamlined body and a radar-reflection amplifying device as well as an engine. However that decoy has not proven to be successful against weapons with an IR searchhead or with a combined infrared and radar searchhead.
It is well-known to defend airborne objects emitting an infrared radiation against missiles equipped with infrared seeker heads, in that upon detection of the approach of a missile one or more pyrotechnic fake target clouds are launched in succession by means of droppable bodies in the air space adjacent the object, the clouds guiding the infrared seeker head of the missile from the object and towards themselves. For example, reference is made to European Patent No. 0 240 819 wherein droppable bodies generating fake targets are placed and ignited in such a manner at specified times in predetermined spatial regions that the generated fake targets lie on a deflection curve at specified intervals in time and space and are to be steered towards in such a manner in succession by the missile that its flight path passes over in the deflection curve and finally in the direction of deflection.
The fake target clouds may comprise burning phosphorus flares, such as plates or strips which are coated with red phosphorus and which are ejected from the droppable body at a predetermined height at the desired point and in so doing are ignited.
However, the goal of the latest development in infrared seeker heads is to make the seeker heads "intelligent" and thus to make them immune to conventional infrared fake targets, i.e., to design them in such a manner that they respond to the object signature, in particular the aircraft signature.
A method to eliminate false targets consists of a frequency analysis by means of the seeker head, which can distinguish between the radiation characteristics of the infrared radiators (for example aircraft engines) of the target that exhibit a comparatively low temperature and the radiation characteristics of a hot fake target cloud. Thus, in summary the known infrared fake target clouds are not in a position to defend an object against missiles equipped with intelligent seeker heads.
IR decoy flares are used on many military aircraft to protect against attack by heat seeking missiles. Flares which are currently in use are made from a solid pyrotechnic composition of magnesium, polytetrafluoroethylene (PTFE) and VITON.RTM. brand fluoroelastomer copolymers or similar synthetic rubber binders. These are commonly called MTV flares and are ejected from an aircraft and simultaneously ignited by the action of a pyrotechnic squib. The burning MTV emits IR radiation that is essentially a spectral continuum attenuated by atmospheric absorption. It is intended that the falling flare will cause a missile seeker head to turn away from the target aircraft. The MTV flares are quite effective against older type missiles that seek heat in a single IR band.
However, modern missiles employ counter-counter measures (CCM). Their more refined seeker heads use two or more spectral bands in an attempt to distinguish between the flare and the aircraft. Both IR and ultraviolet (UV) band may be used. Trajectory discrimination may also be used by some seeker heads and the physical size of the heat source will be become more important in the future as imaging seekers are developed.
Alternatives to MTV flares have therefore been considered in recent years and in particular flares that use the combustion of pyrophoric liquids to generate an intense heat source have been shown to be particularly effective. These are too large and cumbersome to be practical. A pyrophoric flare is disclosed in U.S. Pat. No. 5,136,950.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. .sctn.1.56(a) exists.